A correlation between tail docking length and formation of amputation neuroma

In pig production, piglets are tail docked in order to prevent tail biting later in life. As known in preceding researches, the amputation neuromas may occur at the docked tail tip that altered nociceptive thresholds which causes lifelong pain to pigs. The aim of this study was to investigate the interrelationship between docked tail length and the formation of amputation neuroma associated with the aspects of animal welfare.

A total 300 pig tails were cut off 0.5cm from the tip, and the length and diameter were measured by a ruler. The docked tail length was a distance between 1cm from the root and 0.5cm from the tip, and the diameter was at the 0.5cm from the tip. Cross section was made according to methods by M.S Herskin et al., 2014. . In their research, the intact tail length of crossbred LYD (Landrace x Yorkshire x Duroc) was 30.6 ±0.6 cm (n=65). The sections were examined by Olympus BX50 microscope (Olympus, Tokyo, Japan) at magnifications 4, 10 and 25X. The dimensions of neuromas in the sections were measured by image analysis software (IMTi-Solution Inc., Burlington, Canada). The experimental design was divided into 3 groups according to range of tail length calculated through the referred intact tail length, mentioned above: group L (long, n=58 (19.3%), 15.3 cm ≤ length < 22.95 cm, 25~50% docking), group M (moderate, n=187 (62.3%), 7.65 ≤ length < 15.3, 50~75% docking) and group S (short, n=55 (18.3%), length < 7.65, 75~100% docking). The number of tails with neuromas, the number of neuromas per tail and the mean size of neuromas were measured. Kruskal-Wallis test and Fisher’s exact test of SPSS statistics 21 (IBM Corp., USA) were used for the interrelationship between docked tail length and formation of amputation neuroma.

The total percentage of tails accompanied with neuromas was 72.3% (n=217), the number of neuromas per tail was 0.84 ± 0.64 and the mean size of neuromas was 1,122.30 ± 378.8㎛, respectively. The results of above variables in each group as follow: group L was 70.69% (n=41); 0.93 ± 0.80 and 1,137.57 ± 401.90 ㎛, group M was 78.60% (n=147); 0.88 ± 0.56 and 1,109.03 ± 368.51 ㎛ and group S was 52.73% (n=29); 0.64 ± 0.68; 1,162.57 ± 394.04㎛, respectively. No statistically significance was observed except number of neuromas per tail (p = 0.017).

This study focused on the relationship between docked tail length and formation of neuromas. Neuromas were found throughout all docking lengths, and the extent of neuroma formation was not affected by docking length.

Disclosure of Interest: None Declared.